Worked on stabilizing containerized build and test workflows for Python Cython extensions in the facebook/buck2 and facebook/buck2-prelude repositories. Addressed reliability issues in pyext container build tests by ensuring correct dependency mounting through the addition of the ThirdPartyBuildInfo provider to cython_library. Resolved environment-mismatch crashes, including an ASAN segmentation fault, by refining build constraints to prevent incompatible extension loading. Applied these fixes across multiple repositories to improve test stability and reduce onboarding friction. Leveraged skills in build systems, containerization, and dependency management, with a focus on Python and Cython, to deliver robust cross-repository solutions and facilitate smoother development cycles.